Cancer procoagulant A (CPA), extracted from malignant tissue, is not tissue thromboplastin, but rather a serine protease that initiates coagulation by directly activating factor X. Cancer procoagulant was identified in medium from transformed fibroblasts and extracts of malignant tissue but not in their normal counterparts, suggesting it is unique to malignant transformation. CPA from V2 carcinoma (CPA-V2) has been purified to homogeneity and some of its physical, chemical and enzymatic properties have been determined and an antibody has been developed. The objectives of the proposed research are to complete the studies of the chemical and enzymatic properties of the purified CPA-V2. Cancer procoagulant from several human malignant tissues will be purified and studied to determine if there are CPA isozymes. The immunochemical studies of CPA-V2 antibody will determine its specificity, ability to inhibit CPA activity and its cross-reactivity with procoagulants obtained from other sources. An immunoassay will be developed to quantitate CAP in serum samples of animals and humans with cancer for diagnostic purposes. Another objective of the proposed research is to determine the role of CPA in the neoplastic process. Purified CPA or its antibody will be added to normal and transformed cells in vitro and changes in cell growth and function will be monitored in the presence and absence of fibrinogen to determine the separate and combined effects of CPA and fibrin deposition on these processes. In addition, malignant cell lines with known tumorigenicity or metastatic capacity will be injected into host animals with added pure CPA or its antibody and their tumorigenic or metastatic capacity will be monitored in normal and defibrinated animals. Hosts will be immunized with pure CPA and the tumorigenic or metastatic capacity of the cell lines will be determined in normal and defibrinated animals.